Flip-flop stage control circuits



Sept. 16, 1952 c. M. E. MASSON FLIP-FLOP STAGE CONTROL CIRCUITS Filed Nov. 28, 1950 Patented Sept. 16, 1952 UNITED v STATE s EATENT, OFFICE-f I s; l, i j

v FLIP-FLO? s'rAcE contract. amts Claude Marie Edmond Masson; Paris, France, as-

signor to Societe dElectronique et dAutomatisme, Paris, France, a corporation of France.

Application November 28, 1950, Serial No. 197,863 In France December '7, 1949 The present invention relates to'improvements in control circuits for flip-flopstages arranged in a chain of binary stages constituting a count' ing system, in order to perform a general return of said stages to the rest or normal position by means of one single pulse when the counting operation is terminated.

Any flip-flop stage comprises two electron tubes of at least three electrodes, said tubes being mu tually coupled from anode tocontrol grid by means of time constant-connections. If the said connections have identical characteristics such-a stage has two conditions of 'stabilitydepending upon which tube is nonconducting, theother tube of the pair being simultaneously conducting. One of these conditions may be arbitrarily chosen-as the rest or normal condition. or position. Itis the condition in which all stages are before the application of a series of actuating impulses, which effect a pulse count. The other condition is defined as the operating actuated-condition and is individual for each stage, thechange-over from one condition to the other being effected for each 2 Claims" (Cl.'250'27) stage by applying anactuating pulse to an-I'ap:

propriate electrode. In a counting. chain, the interstage coupling is frequently .obtainedrby means of .a symmetrical circuit extending from the output electrode of, one stageto -both,.triggering electrodes (either grids or cathodes) .oi the next stage. At the end of a count, some-or all stages may be in theactuated stateand must be reset to the state of, rest in readiness'for a fresh counting operation. It is desirable. that this resetting operation be efiected by applying a sin-. gle auxiliary actuating pulse to an appropriate electrode. ofall the stages. Wher the-.interstage coupling is a symmetrical circuitno other auxiliary actuating electrodes are available to the operator than the anodes of the tubes even when the stages comprise tetrodes' or pentodesybecause the use of the screen grids or suppressor grids for such purpose would introduce an uncertainty with regard to the final condition of any stage.v This uncertainty arises from thefact that, while the stage will flip over properly if the resetting impulse is of sufiicient height or amplitude, the tail of the impulse may cause parasitic flip-overs.

One object of the present invention is to pro vide an improved trigger circuit of the kind specifled above having particularly simple and eificient means for resetting it by applying a single impulse to the plate of the tube. f .S'uchresetting meana-according to .the invention, comprise an inductance adapted to be seriesconnected in the high-tension supply to the plate of the constituent tube which is'conductive when the trigger circuit is in the actua'ted'state, said inductance being of value greater than the prod not of its self-capacity and the square of the internal resistance of said tube, and being adapted to be short-circuited whenhotrequired for resetting purposes.

In the application of the invention to a plurality of'cascade-connected stages,- each compris= ing a bi-stable trigger circuit of the kind'above' specified, said inductancemay be common-toall the stages, its value being then greater than the product of its self'capacity'and the square of the effective resistance equivalent to the parallel connection of said internaltube' resistances in all stages.

It will be seen therefore that, in a counter chain of scale-of-two trigger stages, two separate high-tension channels are provided which,

during resetting, areinterconnect'e d by said inductance, thetwo; channels being respectively connected to the'plates of vthe two groupsof tubes of the different stages," namely the group which is conductive and the .group' which is non-con ductive in the state of rest. During a counting" operation, said inductance 'is' short-circuited so that both groups are connected to a high-tension supply ofidenticalvoltage but for resetting the short- 'circuit on said inductance'is' remcve'd by operating a'switch, whereupon the conscduent introduction of said inductance into the circuit, having regard to its value, produces a sharp change in the plate voltage of thatflg'rou'p oft'u'b'es which ought to be non-conductive in the state of rest, 'suchchange of voltage being sufficientto render non-conductive any'tubes of that group p which may have remained conductive at the end of a count; this will flip over any stage conf taining a tube thus rendered non-conductive by making conductive the other tube ofaiiysuch stage, "which will therefore have returned"to.its stateof rest. Other'stages, which atthe'end of the count, were already in the state of res't, re-i inain in that state, and the resetting operation is thus completed. In thisway the aforementioned change of plate voltage effectively acts as aresetting impulse, Without any separate sourceof impulses being requiredfor this purposeand without recourse to the unreliable method of applying a resetting jimpulse to an auxiliary electrode. Before the next counting operation begins, the switch is operated again to short-circuit ,said in: ductance, whereupon the counter is ready to start afresh with all stages in the state of rest.

With reference to the appended drawings:

of two triode tubesI and 2, which are paired by 7 providing, from the anode of one tube to the grid of the other tube, coupling networks I4 and I5, such as for instance paralleled resistancecapacitor networks. The stage is excited at the control grids through resistors 3 and 4 both connected to the actuating lead 6, at a point which is grounded through a bias resistor 5. The cathodes of the tubes are also provided with a common bias circuit I2. Each tube is provided with an anode resistor, 8 for tube I and 9 for tube 2. Resistor 9 is directly connected to the high voltage supply at +HT, resistor 8 is connected to +HT through a circuit comprising in parallel an inductor I0 and a shunting short-circuit II. The output connection of the stage is shown at I.

In normal operation, short-circuiting switch I I is closed, which eifectively connects anode resistor 8 to the high voltage supply. The stage operates by alternatively changing its condition, according to the well-known process, at each pulse applied at 6.

If, at the end of the operation, the stage is in the operating condition (as illustrated, with tube I conducting and tube 2 non-conducting, the reverse arrangement, if preferred, would necessitate the transfer of inductor Ill and its shortcircuit II onto the other anode) resetting to zero is performed by opening contact II. Inductor II) is then inserted between the high voltage source and resistor 8 and the flow of current across it will cause a variation of the potential applied across resistor 8, which variation acts as a resetting pulse, provided inductor I0 is suitably dimensioned.

Considering therefore the illustration'of Fig. 2 it may be seen that the circuit of the flip-flop stage, between the high voltage source and the ground, inductance :0 being activated and switch II open, essentially comprises the parallel impedance network LC (L being the inductance of coil I0 and 0 its natural capacity), in series with resistor R, the value of which is determined by the values of anode resistor 8 and the internal resistance of tube I grounded through resistors 3 and 5 on the one hand and bias circuit I2 on the other hand. Practically in this resistor R, the main element is the internal resistance of the conducting tube, and the remaining parameters are of much less importance. Consequently, in order that the action of inductance Ill be operative, it is sufficient to choose for L a value largely above RFC, for instance from ten to fifty times higher, together with C, the measured capacitance of inductance I0 and R, resistance of tube I, as measured by means of an electron tube meter.

The reason for this is that the critical trigger point of the stage is a function of the ratio of values L/R and l/RC. The above stated condition for the dimensioning of inductor I0 guarantees that in every condition this critical point is overridden.

value of inductance III for general return to the rest condition will then be the Nth part of the above mentioned value; that is:

K being the above cited coefiicient of security (which, if chosen of a large value, as from 10 to 50, makes it possible to obtain a secure resetting operation, the value of the said coefficient not being critical in itself) What I claim is:

1. An electronic pulse operable circuit having a flip-flop stage with two conditions of stability said stage comprising two tubes each having at least three electrodes and time constant connections respectively from the plate of each of the two tubes to the grid of the other tube whereby one tube is conductive when the other tube is non-conductive and vice versa, one of said conditions of stability corresponding to a state of rest and the other condition of stability to an actuated state of said stage, and means for resetting said stage to said state of rest comprising an inductance with means to connect said inductance in the high voltage supply to the plate of said tube which is conductive when said flipfiop stage is in said actuated state, said inductance being of a value greater than the product of its self-capacity and the square of the internal resistance of said tube, and means for short circuiting said inductance.

2. In combination, a plurality of cascade-connected pulse-operable stages each of which is a flip-flop stage with two conditions of stability, each stage comprising a pair of tubes each having at least three electrodes and'time constant connections respectively from the plate of each tube of a pair to the grid of the other tube of the .pair, whereby one tube of each pair is conductive when the other tube of the pair is nonconductive and vice versa, one of said conditions of stability for each stage constituting a state of rest and the other condition of stability constituting an actuated state of said stage, and means for resetting each stage to its state of rest said means comprising an inductance common to said stages via connections from the high voltage supply through said inductance to the respective plates of one tube of each stage said tube being the one that is conductive when the stage is in its actuated state, the value of said common in ductance being greater than the product of its self-capacity and the square of the effective resistance equivalent to the parallel connection of said internal tube resistances in all stages.

CLAUDE MARIE EDMOND MASSON.

REFERENCES CITED The following references are of record in the file of this patent:

UN ITED STATES PATENTS 

